| 摘要 |
PROBLEM TO BE SOLVED: To restrain a shift shock due to overshoot of signal pressure by interposing an orifice restraining shift shock due to variation of signal pressure between an accumulator valve and an actuator. SOLUTION: When line pressure PL from a shift valve flows in a line pressure circuit 20 for performing shifting, while working oil is charged into a hydraulic circuit from an accumulator valve to a band brake servo 2, a passing flow at an orifice 3 is enlarged, and differential pressureΔP is generated across the orifice 3. Hereby, during the charging term of working oil, output pressure P1 is higher than feed pressure P2, and build-up of the feed pressure P2 is relatively delayed to the output pressure P1. Overshoot of accumulator control pressure Pa acting on the accumulator valve as signal pressure is generated before the build-up of the feed pressure P2, because it is generated directly after beginning of shifting. Consequently, overshoot of the feed pressure P2 can be prevented from generating, and shifting can be smoothly controlled.
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